Method of analyzing steel for copper



con nt exceeding Patented Oct. 17, 1944 UNITED STATES PATENT OFFICE METHOD or marinas s'raar. ron

COPP Brown, Pittsburgh, Pa., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jerse! No Drawing. Application April 11, 1942,

Serial No. 438,646

1 Claim. (Cl. 23-230) This invention is concerned with making steel from ferrous material of indete'rminable copper content, such material being exemplified by steel scrap which may contain copper and which cannot be analyzed because of the large numberof pieces involved.

-The steel industry is presented with certain problems in making steel from such material. For instance, when the material is used in the making of non copper bearing steel, copper may be added to the steel and be undetected so as to provide the steel with inexplainable properties which often may be undesired, it being understood that the steel maker's analyzation of such a steel does not include a copper determination. n the other hand, when it is desired to produce a copper bearing steel, the steel maker has no way of knowing how much copper should be added in finishing a steel made partly from scrap, whereby the steel may be produced with a copper I the specified copper range. These circumstances necessitate the scrapping or undesired conversion of many heats of steel today. 1

According to the present invention, a steel making furnace, such as an open-hearth or electricfurnace, is charged so as to include the type of material under discussion, which will usually be steel scrap. The melting and refining practice may be conventional, but prior to finishing the steel it is sampled, this being done so as to obtain a sample truly representative of the metal bath under refinement and after all the charge in the case of a non-copper bearing steel, the

steel being worked is finished as a copper bearing steel; and should it be less than this predetermined value, the steel is finished as a noncopper bearing steel. Furthermore, conventional copper determination methods are used to obtain a series of turbidity values each indicative of a known amount of copper in the steel sample, it therefore being possible for the steel maker to know before finishing the steel, the amount of copper already in the steel, whereby he knows the amount of copper he should add in the case of finishing the steel as a copper bearing product. In these fashions the previously mentioned problems are solved.

As a specific example of the turbidity measuring procedure described, one quarter gram of the steel sample is transferred to a 125 milliliter flask to which is added 2.5 ml. of a perchloric- '20 nitric acid mixture consisting of nine parts of i 60% perchloric acid and one part nitric acid of I to dissolve the gravity. The flask is then heated 1.20 specific steel, and further until fumes vcome out of the flask and crystals form in its bottom. The flask is then cooled and 10 ml. of

stannous chloride solution is added, this solution consisting of 350 gms. of stannous chloride, 200 of hydrochloric acid and water sufficient to make 1000 ml. .The

so flask is then shaken and the solution transferred has been added and melted in the furnace. The

- copper determination does not involve the delicate procedure necessitated by conventional copper determining methods, and it can, therefore, be carried out in the same building housing' the steel making furnace, whereby the results are accessible prior to the time it is necessary-to finish thesteel.

Continuing, should the turbidity of the above solution exceed a value predetermined, by conventional copp r, analyzation methods, as representing the maximum copper content hermisdb e its degree of turbidity'is 40 to a test tube and diluted to 25 ml., whereupon one ml. ,of a 1% starch water-solution is added and the solution mixed. The stannous chloride functions to reduce the cupric form' of copper to the cuprous form which renders the solution turbid, the copper then being present as cuprous thiocyanate, while the tartaric and hydrochloric acids function to dissolve the stannous chloride in the olution to prevent this compound from functions to prevent a crystalline precipitate of copper thiocyanate by causing it to appear in colloidal form.

Light is now passed through this solution in the test tube, and the amount of light passed is photometrically measured and recorded. Preferably a turbidimeter is used, this being a machine having means for positioning the test tube, a light source of fixed, intensity for cast mg a beam through the test tube and aphotoas um absorption bythe connotation-m tube,

cell photometer for mea'suring'the beam after it passes through the'tubes If suh a machine is used, the scale of its-photocell potentiometer should be calibrated in terms of percentage of itself rendering the solution turbid, The starch to rise and for the turbidity to form. A reading is then taken from the dial of the machine which provides the percentage of light absorption of the solution, If the described machine is not used,

it will b necmsary to determine the range between the light absorption by the solution prior to the addition of thiocyanate, and total light absorption, divide this range into hundreds and thereby de e the percentage of light absorption obtained upon measurement of the light passed through the solution after the addition of the thiocyanate.

Having obtained the percentage of light absorption percentage value of the solution, and having previously determined a series of light absorption percentage values produced when following exactly the same procedure, excepting that the steel of known copper content, it is now possible to immediately obtain the copper content of the sample, by comparing this light absorption value obtained, with those known to represent known copper contents. This result is obtained by the described procedure so quickly that it is available dissolved in each instance was degree of turbidity 2,360,644 the machine being adjusted to bring the pointer.

methods, this being particularly so if the sampling was done as soon as the total charge, including all of the material of indeterminable copper content, was melted and adequately mixed to permit accurate sampling. It is to be understood that not only are conventional copper analyzations not made when a non-copper bearing steel is being produced, but this analyzation takes so long that it is necessary to finish the heat prior to the results being obtained, this preventing the use of the conventional method as a guide to the addition of copper even when a copper bearing steel is being made.

The starch solution added to the mixture may be substituted by other colloids, such as gum arabic, for instance. The idea is to provide a material that does not of itself absorb light but which produces a colloidal precipitation aiding the copper cyanate to go into its proper light absorbing colloidally dispersed precipitate form.

I claim:

A method of analyzing steel for copper which includes dissolving a sample portion of steel in a perchloric-nitric acid solution, then adding a water solution of stannous chloride and tartaric and hydrochloric acids to the solution in which the sample is dissolved and mixing therewith and finally adding a water starch solution and sodium thiocyanate thereto and mixing therewith, whereby to produce a solution having a proportional to the copper content of the steel.

' WILLIAM D. BROWN. 

